How long does it take for carbon monoxide alarm to go off?

Author: Marjory Ruecker  |  Last update: Sunday, March 9, 2025

It can take a standard carbon monoxide detector one hour to alert at concentrations of 70 ppm and below. CO detectors will respond to extremely high concentrations of 400 ppm and above in as little as four minutes.

How long does a carbon monoxide detector take to detect?

If detected over the course of a few hours, carbon monoxide at 70 ppm will trigger an alarm. At the other end of the spectrum, dangerous concentrations above 400 ppm will do the same after just a few minutes.

Do carbon monoxide detectors go off immediately?

Carbon monoxide levels must build up in your home before an alarm goes off. Since an alarm measures the amount of carbon monoxide over a certain period, it could take your detector hours to go off or 10 or 20 minutes if you have a lot of gas building up in your home.

How long do you have to be exposed to carbon monoxide to be affected?

You may lose balance, vision and memory and even consciousness. This can happen within 2 hours if there's a lot of carbon monoxide in the air. The smaller an animal or person is, the faster they'll be affected. Pets are often the first to show symptoms.

What triggers a carbon monoxide alarm?

Any fuel-burning appliance that is malfunctioning or improperly installed. Furnaces, gas ranges or stoves, gas clothes dryers, water heaters, portable fuel-burning space heaters, fireplaces, generators, and wood burning stoves. Vehicles, generators, and other combustion engines running in an attached garage.

What to Do When Your Carbon Monoxide Detector Goes Off

What if the carbon monoxide alarm goes off but no fire?

False or nuisance alarms are when your smoke detector or CO alarm goes off, but there is no presence of smoke or carbon monoxide in your home. However, if your smoke or carbon monoxide detector sounds indicating an emergency and you are not certain it is a nuisance alarm, evacuate the home and call 9-1-1.

How much carbon monoxide before alarm goes off?

"According to UL Standard 2034, home carbon monoxide detectors must sound a warning before carbon monoxide levels reach 100 parts per million over 90 minutes, 200 parts per million over 35 minutes or 400 parts per million over 15 minutes.

What are two warning signs of carbon monoxide poisoning?

The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. CO symptoms are often described as “flu-like.” If you breathe in a lot of CO, it can make you pass out or kill you.

Why did my carbon monoxide alarm go off and then stop?

This could be due to a faulty device, old batteries, or just dust buildup in the unit itself. It's better to be safe than sorry. If your alarm sounds, it's important to call emergency responders. They can tell you if you're experiencing a false alarm.

Can I go to sleep after carbon monoxide exposure?

Carbon monoxide is dangerous because a person may not recognize drowsiness as a symptom of poisoning. Consequently, someone with mild poisoning can go to sleep and continue to breathe the carbon monoxide until severe poisoning or death occurs.

What can falsely set off a carbon monoxide detector?

Common causes of false alarms of carbon monoxide:
  • Close to cooking sources (10 feet minimum)
  • Close to sources of humidity (10-20 feet)
  • Near fireplaces.
  • Near water heaters.
  • Near furnaces.
  • Located in a poorly ventilated location like a garage, kitchen, or closet.

Should I call 911 if my carbon monoxide alarm goes off?

My carbon monoxide alarm is sounding. What should I do? Call 911 and report what is happening. Immediately leave your residence and wait for the fire department to arrive.

How long does it take to get carbon monoxide out of your system?

The carbon monoxide in your body leaves through your lungs when you breathe out (exhale), but there is a delay in eliminating carbon monoxide. It takes about a full day for carbon monoxide to leave your body. 1.5 HOW CAN CARBON MONOXIDE AFFECT MY HEALTH?

What will my alarm do if it detects carbon monoxide?

When the carbon monoxide alarm senses a dangerous level of CO gas, the unit will emit a loud alarm pattern. The alarm pattern is four short beeps – followed by five seconds of silence – followed by four short beeps.

How long to air out a house after carbon monoxide?

If your home has a well-functioning ventilation system, the carbon monoxide should be cleared within 30 minutes. If the ventilation is inadequate, it can take several hours to clear.

Will a carbon monoxide detector detect small amounts?

Sensitivity and Calibration Issues: Most carbon monoxide detectors are designed to alert you only when CO levels reach a certain threshold, typically 70 parts per million (ppm) over a short period. However, levels lower than this can still be harmful, especially with prolonged exposure.

What if carbon monoxide alarm goes off but no fire?

Your carbon monoxide alarm is going off for one of the following reasons: It is doing its job properly and detects CO pollution in the air. It is a false alarm caused by other household items. The detector is malfunctioning or the batteries need changing.

Does the fire department charge to check for carbon monoxide?

In most areas, the fire department does not charge to respond to carbon monoxide alarms or to check for the presence of CO in a residence. However, policies can vary depending on the jurisdiction or specific fire department. It's always a good idea to contact your local fire department for specifics on their policies.

What does 4 beeps mean on carbon monoxide?

What Does an Emergency Alarm Chirp Mean? This meaning is probably the most self-explanatory. When your carbon monoxide detector chirps 4 times in a row and pauses, this means it has detected unsafe levels of carbon monoxide. This means your entire household should evacuate immediately and seek fresh air.

What to do if a carbon monoxide alarm goes off and then stops?

If you have a carbon monoxide detector chirping and then it stops, it's important to take the situation seriously, even if the alarm is no longer sounding. Even if the alarm has stopped, get everyone out of the home to a place with fresh air.

How to test a carbon monoxide alarm?

How to test your carbon monoxide detectors to ensure they are working properly? To test your carbon monoxide detectors, press and hold the test button on the alarm. The detector will sound 4 beeps, a pause, then 4 beeps for 5-6 seconds. Refer to the user manual for your specific model.

What does slow carbon monoxide poisoning look like?

Symptoms of carbon monoxide poisoning may include: Breathing problems, including no breathing, shortness of breath, or rapid breathing. Chest pain (may occur suddenly in people with angina) Coma.

Will opening a window help with carbon monoxide?

If you experience symptoms that you think could be from CO poisoning: DO GET FRESH AIR IMMEDIATELY. Open doors and windows, turn off combustion appliances and leave the house.

Should I call the fire department if the carbon monoxide alarm goes off?

If your CO detector goes off and you feel ill, leave the house and call 911 or the local fire department. If you do not feel ill, push your detector's reset button. If the alarm goes off again after a few minutes, open the windows, leave the house and call 911 or the local fire department.

How quickly do carbon monoxide detectors work?

It can take a standard carbon monoxide detector one hour to alert at concentrations of 70 ppm and below. CO detectors will respond to extremely high concentrations of 400 ppm and above in as little as four minutes.

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